This invention relates to an etching processing method and, more specifically, to an etching processing method for performing an etching processing on a resin member with the use of a desmear liquid comprising an alkaline permanganate etching liquid.
In the field of wiring boards, in order to improve peeling strength of a copper film formed on a surface of a resin member of a resin plate or the like by copper plating, etching is performed on the surface of the resin member for roughening the surface.
Such roughening is generally performed by way of an etching processing on the resin member surface, wherein the resin member is dipped into a desmear liquid comprising an alkaline permanganate etching liquid.
A degree of irregularity of the resin member surface relates to the thus-roughened resin member and the peeling strength of the copper film formed by the copper plating. Since it is difficult to check the irregularity degree of the resin member surface during the etching processing, the irregularity degree is controlled by way of an etching time depending on an etching rate of the desmear liquid. Therefore, the desmear liquid is required to have an appropriate etching rate.
When the etching processing of dipping the resin member into the desmear liquid is performed for a certain times, carbonate ions are accumulated in the desmear liquid as described in Patent Publication 1. In the desmear liquid in which carbonate ions are accumulated, the etching rate is accelerated to be out of the appropriate etching rate range, thereby making it impossible to control the degree of irregularity to be formed on the resin member surface. Therefore, the desmear liquid in which a predetermined amount of carbonate ions are accumulated is discarded.
The discarded desmear liquid is reused as proposed in Patent Publication 1 by adding barium chloride to the desmear liquid to change the carbonate ions in the desmear liquid into hardly soluble barium carbonate and then removing the barium carbonate by ultrafiltration.    [Patent Publication 1] JP-A-2001-156428
According to Patent Publication 1, it is possible to reuse the desmear liquid that is not capable of controlling the degree of irregularity to be formed on the resin member surface due to the accelerated etching rate caused by the carbonate ion accumulation.
However, in view of the fact that it is necessary to stop the etching processing during desmear liquid replacing work, it is considered that it is possible to improve operation efficiency of the etching processing when life of the desmear liquid is lengthened as long as possible.
Also, even when the desmear liquid has the predetermined etching rate, the adjustment of time for dipping the resin member into the desmear liquid that is conducted for adjusting the degree of irregularity to be formed on the resin member surface makes etching processing management complicated and also complicates managements in a pre-processing and a post-processing of the etching processing.